Re: setup_git_directory_gently contract question?

["Ciprian Dorin Craciun" <ciprian.craciun@gmail.com>]

On Wed, May 28, 2008 at 1:46 AM, Junio C Hamano <gitster@pobox.com> wrote:
> "Ciprian Dorin Craciun" <ciprian.craciun@gmail.com> writes:
>
>>     Is the function setup_git_directory_gently supposed to change the
>> current working directory, or should it keep the initial one?
>>     What is the meaning of nongit_ok?
>
> Most commands that work from subdirectory use setup_git_directory()
> interface, because major parts of the guts of the git internal want you to
> be at the top of the work tree (e.g. so that you grab a path out of the
> index, and be able to open(2) or lstat(2) that path).  A normal sequence
> for a command is: (1) use setup_git_directory() to learn "prefix", (2) use
> get_pathspec() and/or prefix_path() to add "prefix" to the paths given
> from the command to make it a path relative to the work tree, (3) do its
> thing.  setup_git_directory() chdir's up to the top of the work tree for
> this reason.
>
> Some commands can optionally work from even outside a git repository, but
> they would want to operate the same way as other comands, when they are
> started within a git repository.  In such a case, you use "gently"
> variant, and give a pointer to int to store an additional return value to
> signal you if you are inside a git repository or outside.
>
>  * When NULL is given as nongit_ok to gently(), it does not behave gentle
>   at all.  Outside a git repository it dies loudly.
>
>  * If you are inside a git repository, it behaves pretty much the same as
>   setup_git_directory().  "*nongit_ok" is set to zero to signal that you
>   are inside a git repository.
>
>  * If you are outside a git repository, *nongit_ok is set to non-zero so
>   that the caller can tell that it is not in any git repository's work
>   tree.  There is no need to chdir (nor a sensible place to chdir to) in
>   this case, so it doesn't.
>
> The caller thinks of the parameter as "are we operating in non-git mode?"
> boolean, and the callee (i.e. setup_git_directory_gently()) thinks of it
> as "is it ok to be called outside a git repository?" (if it is NULL, the
> caller expects to be inside a repository and wants it to barf otherwise).
> That is why caller's variable are often called "int nongit", and the
> callee's parameter is called "int *nongit_ok".

    Thank you for your complete answer.

    I would propose that these comments to be added to the
Documentation/technical/... directory, (or in the setup.c file), so
that further developers will have this information.

    Thanks again,
    Ciprian.